High Stress Research Articles

Finite element analysis of occlusal stress in cervical dentin: effects of thickness and cross-section

Background & objectiveThe cervical region of dentin plays a crucial role in the distribution of masticatory forces, with vertical root fractures often initiating and spreading from this area. This study investigates the distribution of occlusal stresses in the cervical region of root dentin, considering varying thicknesses and cross-sections, using Finite Element Analysis.Materials & methodsSections from central and premolar teeth were imported into CAD to create 3D models. The tooth structure and surrounding tissues were modeled using mechanical properties such as Young’s modulus and Poisson’s ratio. Four cross-sectional shapes—circular, oval, sand clock, and kidney—were designed. A force of 50 Newtons, representing the occlusal force of the opposing tooth, was applied to the palatal surface of the models at a 60° angle for anterior teeth and a 45° angle for premolars. The stress distribution in the cervical dentin was then analyzed.ResultsVon Mises stress values indicated that stress points were highest in the kidney, sand clock, oval, and circular cross-sections, respectively. Increased thickness of the residual dentinal wall resulted in reduced maximum and minimum stress and a smaller area of stress regions. In all cross-sections, the minimum and maximum stress points were predominantly on the palatal and buccal sides of the cervical dentin, respectively.ConclusionThe study demonstrated that stress distribution in teeth varies with different root cross-sections, with higher stress observed in the sand clock and kidney cross-sections. Thinner dentin in the cervical region leads to greater stress concentration, especially in the buccal area of the tooth.

Evaluation of the VAT Exemption Facility Policy for Universities Reviewed from the Cost of Compliance

To optimize state revenue, the Indonesian government continues to implement tax extensification and intensification programs. Under Law Number 7 of 2021 (Harmonization of Tax Regulations Law or UU HPP), educational services are reclassified as Value-Added Tax (VAT) objects with exemption facilities, requiring universities and other educational service providers to register as Taxable Firms (PKP). This regulatory change obliges them to administer VAT invoices without the right to credit input tax, which was not the case under the previous regulation where educational services were categorized as non-VAT objects. As a result, this policy significantly increases the compliance cost for educational institutions. The objective of this study is to examine the rise in compliance costs—specifically direct monetary costs, time costs, and psychological burdens—experienced by educational service providers due to the VAT regulation changes. This research adopts a qualitative approach through literature review and comparative analysis with international best practices in other countries that apply VAT to education. The findings reveal that although the VAT exemption facility aims to maintain accessibility, the administrative burden placed on educational institutions has increased, particularly in relation to invoice issuance, system adjustments, and internal training. These factors contribute to higher operational costs and stress levels among administrative personnel. The study highlights the need for clearer technical guidelines and support systems to reduce compliance burden. It also provides insights for policymakers in balancing fiscal objectives with the operational realities of the education sector.

Biomechanical Evaluation of Cantilevered 2-Unit Implant-Supported Prostheses: A 3D Finite Element Study.

To assess the biomechanical performance of cantilevered 2-unit implant-supported prostheses with zirconia and polyetherketoneketone (PEKK) under 3 loading conditions. A cone beam computer tomography (CBCT) scan of an edentulous mandible was segmented using Mimics software and refined in 3-Matic software to create trabecular and cortical bone structures. Implant CAD files were integrated using SolidWorks software, generating 4 models with varying implant positions: M1 (first premolar implant supporting a second premolar), M2 (second premolar implant supporting a first premolar), M3 (second premolar implant supporting a first molar), and M4 (first molar implant supporting a second premolar). Prostheses were constructed from zirconia or PEKK. Finite element analysis (FEA) in ANSYS software simulated static loading: vertical (100 N) and oblique (30° and 45°, 50 N). von Mises stress and total deformation were analyzed. Vertical loading showed the highest von Mises stress at cantilever connectors, with M3 displaying the highest cortical bone stress (117 MPa). Zirconia models had slightly higher prosthetic stress, while PEKK models exhibited greater implant and cortical bone stress. Oblique loading caused higher stress in implants and prostheses but remained below yield limits. Maximum deformation was under 25 micrometers for the implant and bone, and 65 micrometers for the prosthesis. Single implants can support 2-unit cantilevered prostheses when additional implants are unfeasible. The location of the cantilever has minimal impact compared to its size, as a larger cantilevered part increases stress. Zirconia better resists bending forces and reduces implant stress compared to PEKK. This study guides prosthodontists in designing 2-unit implant-supported prostheses, emphasizing that multiple implants optimize stress distribution, and that zirconia is preferable for cantilevered designs.

Higher gender role stress and depressive severity increase suicide risk among male military service members and veterans.

Higher gender role stress and depressive severity increase suicide risk among male military service members and veterans.

Effect of pre-activation force on active force generation in skeletal muscle.

Effect of pre-activation force on active force generation in skeletal muscle.

Premed pressure: examining whether premed students experience more academic stress compared to non-premeds.

Academic stress is one of the primary factors threatening university students' well-being and performance. Undergraduate students who are working toward applying to medical school, defined as being on the premedicine or "premed" pathway, are suspected to have higher academic stress compared to their peers who are not premed. However, what factors contribute to academic stress for premed students is not well understood. We sought to answer the following: Do undergraduates perceive that premeds have higher, the same, or lower stress than nonpremeds? How do academic stress levels between these groups actually differ? What aspects of being premed cause academic stress? Who has left the premed track and why? We surveyed 551 undergraduates from one large institution in the United States and answered our research questions using descriptive statistics, chi-squares, and linear regressions. Overwhelmingly, participants perceived that premed students experience greater academic stress than their counterparts, yet we found no significant differences in academic stress reported among students in our sample (P > 0.05). Premed students reported that their academic stress was exacerbated by not feeling competitive enough to get into medical school and by needing to maintain a high grade point average (GPA). Furthermore, students with lower GPAs were more likely to leave the premed track compared to those with higher GPAs (P = 0.005). Students reported leaving the premed track because another career appeared more interesting and because of the toll the premed track took on their mental health. In conclusion, our findings can inform instructors and universities on how to best support premed students.NEW & NOTEWORTHY Participants perceived that premed students experience greater academic stress than their counterparts; however, we found no significant differences in academic stress reported among students in our sample (P > 0.05). Students with lower GPAs were more likely to leave the premed track compared to those with higher GPAs (P = 0.005).

Salivary chromogranin A levels relate to fatigability after waking up.

Salivary chromogranin A levels relate to fatigability after waking up.

Which should be targeted first? The comorbidity of sleep disturbances and anxiety symptoms among adolescents: Cross-sectional and longitudinal network analyses.

Which should be targeted first? The comorbidity of sleep disturbances and anxiety symptoms among adolescents: Cross-sectional and longitudinal network analyses.

Dynamic simulation of knee joint mechanics: individualized multi-moment finite element modelling of patellar tendon stress during landing.

Dynamic simulation of knee joint mechanics: individualized multi-moment finite element modelling of patellar tendon stress during landing.

Enhancing an existing composite model to estimate MSW settlement during the filling and post-closure phases in both warm and cold regions.

Enhancing an existing composite model to estimate MSW settlement during the filling and post-closure phases in both warm and cold regions.

Optimizing fatigue life predictions for scraper rings: classical vs modern models

This study provides a comprehensive comparative evaluation of classical and modern predictive models for fatigue life in scraper rings of internal combustion engines, which operate under high thermo-mechanical stresses. Accurate fatigue life predictions are essential for optimizing engine component design, preventing both over- and under-engineering while ensuring long-term reliability. The effectiveness of both traditional models and newer advanced approaches was analyzed using loading profiles that replicate real-world engine operating conditions. Results indicate that stress-life models offer more reliable predictions for high-cycle fatigue scenarios, while strain-life models perform better under low-cycle fatigue conditions. Furthermore, fracture mechanics models show great promise in predicting crack propagation and identifying failure mechanisms. Detailed inspections and Légraud-Poirier (LP) tests confirmed fatigue-induced cracking at critical locations of the scraper rings, emphasizing the importance of incorporating multi-axial loading in fatigue assessments. The findings underscore the necessity for using comprehensive loading profiles and thorough inspections to enhance the accuracy and dependability of fatigue life predictions, which are critical for improving the performance and durability of engine components.

Exploring the Molecular Mechanisms of Fisetin in Treating Periodontitis Through Multiomics and Network Pharmacology.

Exploring the Molecular Mechanisms of Fisetin in Treating Periodontitis Through Multiomics and Network Pharmacology.

Effects of temperature and salinity on CO2 fluxes dynamics and respiration metabolism in the sea cucumber Apostichopus japonicus (Selenka).

Effects of temperature and salinity on CO2 fluxes dynamics and respiration metabolism in the sea cucumber Apostichopus japonicus (Selenka).

The interplay between Ca2+ and ROS in regulating β-carotene biosynthesis in Dunaliella salina under high temperature stress

The interplay between Ca2+ and ROS in regulating β-carotene biosynthesis in Dunaliella salina under high temperature stress

Genome-wide identification of aquaporin and their potential role in osmotic pressure regulation in Ruditapes philippinarum.

Genome-wide identification of aquaporin and their potential role in osmotic pressure regulation in Ruditapes philippinarum.

Protective role of medium-concentration selenium nanoparticles against high salinity-induced oxidative stress in Crassostrea hongkongensis gills and hepatopancreas.

Protective role of medium-concentration selenium nanoparticles against high salinity-induced oxidative stress in Crassostrea hongkongensis gills and hepatopancreas.

Nitrate enrichment exacerbates microbiome and metabolism disturbances of the coral holobiont under heat stress.

Nitrate enrichment exacerbates microbiome and metabolism disturbances of the coral holobiont under heat stress.

Methyl jasmonate regulates panicle morphogenesis by mediating the negative effects of high temperature stress on carbon and nitrogen allocation and utilization

Methyl jasmonate regulates panicle morphogenesis by mediating the negative effects of high temperature stress on carbon and nitrogen allocation and utilization

Insight into Ca2+- inositol 1,4,5-trisphosphate receptor 2 (IP3R2)-mediated unfolded protein response and apoptosis in scallop Patinopecten yessoensis under high temperature stress.

Insight into Ca2+- inositol 1,4,5-trisphosphate receptor 2 (IP3R2)-mediated unfolded protein response and apoptosis in scallop Patinopecten yessoensis under high temperature stress.

Fabrication of cost-effective Ni-based metallic composite columnar catalyst on stainless steel electrode via stress release-assisted electrochemical micro-machining for water electrolyzer.

Fabrication of cost-effective Ni-based metallic composite columnar catalyst on stainless steel electrode via stress release-assisted electrochemical micro-machining for water electrolyzer.